* David Hensle was head of quantitative credit unit
* Hensle replaced by Jamey Thompson
NEW YORK, June 8 (Reuters) - Ken Griffin's Citadel Investment Group dismissed a high-level credit trader in April, even though his portfolio had recorded gains for the year, according to two people familiar with the departure.
David Hensle, who was the head of the quantitative credit business, left the Chicago-based hedge fund in mid-April.
Citadel confirmed Hensle's departure but declined further comment. Efforts to reach Hensle through the Massachusetts Institute of Technology alumni association were not immediately successful.
The quantitative credit unit invests in various systematic credit trading strategies and in credit instruments such as bonds, single-name credit default swaps (CDS) and index CDS in the United States and Europe.
The group is now being run by Jamey Thompson, a portfolio manager in the credit business who joined Citadel in 2008. The firm's fundamental credit group has been folded into Thompson's unit in recent months.
The credit books contribute to Citadel's flagship funds, Kensington and Wellington, which have gained about 7.5 percent for the year through May, according to a person familiar with the numbers.
Hensle's credit portfolio was in positive territory at the time he was let go, according to the source, and the portfolio had recorded flat to slightly positive gains in 2011.
Hensle, who previously headed the U.S. liquid structured credit market-making unit at Bank of America Corp, joined Citadel in 2006.
In 2009 he and another manager, Becket Wolf, replaced structured credit head Chris Boas, who had been elevated to the role of global head of credit markets in the firm's securities business, which itself was later shuttered. Boas left Citadel in early 2011.
It has been a volatile few years for Griffin's firm, which manages $12 billion in assets. Its main funds lost roughly 50 percent during the financial crisis and Griffin's dream to build an investment bank alongside the hedge fund to rival Goldman Sachs Group Inc and Morgan Stanley ended before it had begun in 2011.
This year, Griffin has had better results for investors. In January, he said Citadel's flagship Kensington and Wellington funds had fully recovered from the steep losses incurred during the financial crisis.